Noisy Gearbox-update, result!

[al pushpak]

Hi, got a bit noisy gearbox when the scooter is on tick over which seems louder around the rear hub side , doesn't seem quite as bad with a bit of throttle, I've checked the 1st gear shim with some feeler gauges & it's within the tolerances, all the bearings & endplate bush are new,the gearbox is an Indian gp 200 from SR, the endplate is the one that came with casing so is matched,chain is a new iwis type with brand new crown wheel & bearing bush, the only bearing that isn't new is the rear hub one but it's a good quality used Italian one, everything seems to work fine , would just be nice to get to the bottom of this noise thanks for any info

[Knowledge]

Does the noise at tick-over disappear when the clutch is pulled in?

[al pushpak]

No, the noise is still there when I pull clutch in aswell I've had another quick look & the 1st gear cog does move up & down a little behind the endplate, I have several of the large shims so maybe I need to try some of these in there

[HxPaul]

Does the noise disappear when the clutch is pulled in and the scooter is put into gear?

[al pushpak]

Yes, Paul I did try that & it wasn't "as noisey" but still there a bit ,think I will have to pull it all out again

[Tractorman]

Sent you a PM on another forum.

[al pushpak]

Hi, had another go at trying to get to the bottom of my rattling sil gp 200 gear box on tickover ( also had this on Italian gearboxes over the years with the noise disappearing when clutch is pulled in) but still not solved it so I have conceded defeat, all parts good,no serious wear, gearbox shimmed correctly etc, gearbox & clutch operate as they should with no problems,so I was just wondering if there was an oil that meets Lambretta spec that was maybe a little thicker & would maybe quiet things down a little ? thanks for any info

[al pushpak]

Hi, spent the best part of the weekend having another go at trying to sort my noisey gearbox. I got hold of another sil gp 200 gearbox off a mate even though mine looked ok with very little wear,fitted a new endplate bearing,layshaft & cluster bearings .I've also checked my layshaft circumference where the cogs run with another one by measuring them with digital vernier gauges & there's no difference. I fitted the new box,all shimmed up ok & even though it does sound a little quieter the noise is still there & disappears when the clutch is pulled in so I've had to concede defeat unless someone has any more ideas or info cheers

[CHRIS in MARGATE]

I meant to ask you this last week. Are you by chance using an older style crown wheel/rear sprocket with the torsion springs in?
Also are the rivets tight on the clutch spider ?

[al pushpak]

Hi Chris , I'm using the later type crown wheel (solid type) that uses the brass bush, it's definitely quieter with the new box , but no way near as quiet as my other scoot that also runs a sil gearbox! thanks again

[HxPaul]

When the clutch is pulled in and you engage gear,the only thing running is the sprockets,chain and clutch corks,everything else is stationery.

[holty]

When the clutch is pulled in and you engage gear,the only thing running is the sprockets,chain and clutch corks,everything else is stationery.

i agree with what paul is saying here, if its still noisey then the problem must be related to chain or sprockets as you have said new crownwheel bearing fitted so it cant be that, is the chain catching the bottom chain guide or a sprocket, i have had chain catching on the bearing track in the backplate, it must be driving you mad, i do hope you find the cause and let us know what it was.

[NorthernJordan]

It sound like you have replaced almost all conceivable parts.

I'd say there is three options:
1. It's normal and the noise is acceptable.
2. It's slightly noisy and all the new components need bedding and oil circulating around them to quieten down.
3. Something somewhere is rubbing/catching.

If noise is significant as you suggest I'd trace all obvious points with some white paint to see if something is actually rubbing/catching. The contact making the noise could be minor and therefor not leaving any obvious signs of wear.

[al pushpak]

Hi, thanks for your input guys, the noise does disappear when the clutch is pulled in, which seems to point to the gearbox, I've thoroughly checked everything,measured & compared layshaft circumferences, checked the cogs for wear,replaced bearings etc,it does seem a little quieter but not as quiet as my other scoot running an identical gearbox & sprockets think I will just have to put it down to it being a noisy gearbox & live with it for now thanks again

[al pushpak]

Hi all, quick update on the noisy gearbox problem I've been experiencing, after trying all the suggestions & fitting different parts ,I acquired a good 2nd hand Italian li 125 box to try, fitted it today with the sprocket combo that's suited for my ts & it's loads quieter !! no idea why the Indian box I had in was louder when I run an identical one in my other scoot thats much quieter but it's definitely solved the problem thanks again for all your advice

[maddogmadox]

Hi Al pushpack
I suggest you might want to look at the first gear cog on the GP gearbox you have, as this may be the cause of all the noise, i have come across two brand new purchased gp200 gearbox's in the last few months that were causing a lot of noise when installed and running. This was down to the first gear being around three mm too small across it's diameter when compared to the correct size GP200 1ST gear an original GP200 first gear is 117mm across it's diameter, the two that i found noisy were around 114mm across the diameter. Both these new GP200 gearbox's were purchased from different suppliers, one of the gearbox's was even purchased as a completed blister pack sealed set . as from the pictures you will see the old original first gear meshes with the christmas tree correctly and on the other picture the new incorrect sized GP200 first gear is a very bad fit and causes a lot of noise. As i said both examples i found of this were from completely different suppliers who genuinely did not know there was an issue until it was pointed out to them,

It took a lot of messing around to find where the noise was coming from as these were two brand new built engines with all new parts i was helping two friends with them and they both bought brand new GP 200 gearboxs from different sources , So there's a good chance there are a few of these incorrect sized first gears knocking about in recently built engines, with people wondering why it's noisy as hell in first gear

first pic is the brand new incorrect size first gear .. the second pic is the correct size first gear you can see how bad the mesh fit is and it's no wonder it was noisy

[ToBoldlyGo]

Wow! They say a picture paints a thousand words. That's quite a shocker actually.

[al pushpak]

Hi maddogmadox, thanks for your in-depth thread reply, some very interesting information & photos there ! when I was trying to sort out my sil gearbox I must have removed & refitted it several times & I never noticed on any occasion the gap like you experienced in your photos, so after reading your reply I nipped out to the garage, dug out my sil gearbox & armed with my digi vernier gauges measured my 1st gear cog, unfortunately/fortunately it measures 117 across its diameter ! so in my case my noise still remains a mystery thanks again though

[maddogmadox]

no problem Al . not a cure to your issue but i am sure it will help someone along the line